Various methods of updating map data of a map display system such as a vehicle navigation system are proposed. In JP 2005-3700A, for instance, a map data is updated by retrieving a map updating data through a communication network.
In a case of traveling to a travel destination such as sightseeing, spots and the like in accordance with a travel road guidance of a vehicle navigation system, a vehicle driver usually takes a main road such as an expressway or a state road and then takes a narrow road near the destination. In this case, a map data of the navigation system only needs the latest information about the main road with respect to area sections or zones (e.g., meshes) up to the destination, and does not need information about narrow roads around the main road. By delivering a map updating data without such unnecessary information, the amount of map updating data, communication cost and delivery time can be reduced.
It is therefore proposed that an information center has two types of map data. One is a latest map data including all roads and the other is a map data that includes latest information about main roads without narrow roads. By delivering map updating data from the information center in accordance with objectives or applications of a user, a map data of an area which a user needs can be updated efficiently.
For reducing the amount of map updating data, communication cost, delivery time and the like, it is further proposed to deliver the map updating data as difference information that is extracted as a difference of the latest map data from the previous map data.
The information center may thus have two types of map updating data. One is an all-road updating data that is a difference of all-road map data relative to all-road map data of all roads, and the other is main-road updating data that is a difference of a main-road map data relative to the all-road map data. The all-road updating data or the main-road updating data may be selectively delivered from the information center in accordance with objectives or applications of a user, and the map data of the map display system may be updated with the delivered map updating data. This map updating data delivery will cause complication of map updating data that is to be managed in the information center.
One example of version-up of a map data, that is, updating a map data, is shown in FIG. 9 as a sequence of updating a map data. In this figure, Va.m indicates a map data version number. In which “a” indicates a version number of an all-road map data and “m” indicates a version number of a main-road map data.
In FIG. 9, it is assumed in the information center that a main-road map data V0.1 is updated or generated first relative to an original version of an all-road map data V0.0 of all roads in the original state. Then, another main-road map data V0.2 is generated. Next, an all-road map data V1.0 is updated or generated relative to the all-road map data V0.0 in the original state. The all-road map data is generated by extracting a difference relative to the previous map data, that is, as difference information relative to a corresponding all-road map data in the previous state. The main-road map data is generated similarly as difference information relative to a corresponding main-road map data in the previous state.
When a map display system of a first vehicle requests updating to the all-road map data V1.0, for instance, the information center only needs to have a map updating data D1, which is a difference between the all-road map data V0.0 and the all-road map data V1.0.
In another case, a map display system of a second vehicle requests updating to the all-road map data V1.0 under the condition that the map data in the second vehicle has already been updated once with the main-road map data V0.1. In this case, the information center needs to have a map updating data D2, which is a difference between the main-road map data V0.1 and the all-road map data V1.0.
In still another case, a map display system of a third vehicle requests updating to the all-road map data V1.0 under the condition that the map data in the third vehicle has already been updated twice with the main-road map data V0.1 and the main-road map data V0.2. In this case, the information center needs to have a map updating data D3, which is a difference between the main-road map data V0.2 and the all-road map data V1.0.
Thus, the information center must manage each version of the all-road map data and of the main-road map data as difference information D. The information center further must have a multiple difference information D such as D1, D2, D3 of the vehicles depending on the update state in the vehicle. Thus, the information center must have a variety of difference information in correspondence to each version of the all-road map data and the main-road map data. This will complicate management of map updating data in the information center.